Re: [Qemu-devel] [PATCH v2 1/2] iotest 033: add misaligned write-zeroes test via truncate

[Anton Nefedov <anton.nefedov@virtuozzo.com>]

On 12/2/2018 6:54 PM, Alberto Garcia wrote:
> On Mon 12 Feb 2018 02:14:00 PM CET, Anton Nefedov wrote:
>> +# Trigger truncate that would shrink qcow2 L1 table, which is done by
>> +#   clearing one entry (8 bytes) with bdrv_co_pwrite_zeroes()
>> +
>> +echo
>> +echo "=== Test misaligned write zeroes via truncate ==="
>> +echo
>> +
>> +CLUSTER_SIZE=$((64 * 1024))
>> +L2_COVERAGE=$(($CLUSTER_SIZE * $CLUSTER_SIZE / 8))
>> +_make_test_img $(($L2_COVERAGE * 2))
> 
> If my numbers are correct, that's a 1GB image. For qcow2 this is not a
> problem but I wonder if it's ok to create such large images for other
> formats (for raw they should be sparse by default, but still).
> 
> Berto
> 

Good point. Actually even 512 byte clusters will work here, resulting
in a just 64k image.